feat(examples): add embedded GPIO tool, auto-load kernel modules, and fix I2C CUSE adapter

- Add generic-gpio-embedded tool using libgpiod to inspect, read, set, and monitor GPIO lines
- Add examples/run_all.sh to build and validate all example applications
- Add Makefile for generic-uart-embedded tool
- Fix I2C CUSE adapter lifecycle parent PID check when executed via sudo/pkexec
- Auto-load cuse and gpio-sim kernel modules during sudo session in run.sh
- Include gpio-sim adapter in dev.sh and gpio_tool in build.sh and install

Author: Hakan Kaya

adapters/i2c-cuse/main.c

@@ -57,20 +57,23 @@ static void *make_device_accessible(void *argument) {
 }
 
 static int configure_lifecycle(vds4e_i2c_config_t *config) {
+  if (prctl(PR_SET_PDEATHSIG, SIGTERM) != 0) {
+    perror("failed to configure parent-death cleanup");
+    return -1;
+  }
+
   if (config->parent_pid > 0) {
-    if (prctl(PR_SET_PDEATHSIG, SIGTERM) != 0 ||
-        getppid() != config->parent_pid) {
-      return -1;
-    }
     pthread_t watcher;
     if (pthread_create(&watcher, NULL, watch_parent, &config->parent_pid) != 0) {
+      perror("failed to start parent watcher");
       return -1;
     }
     (void)pthread_detach(watcher);
   }
 
   pthread_t permissions;
   if (pthread_create(&permissions, NULL, make_device_accessible, config) != 0) {
+    perror("failed to start permissions worker");
     return -1;
   }
   (void)pthread_detach(permissions);

build.sh

@@ -90,6 +90,13 @@ echo "Building generic UART Embedded Linux tool..."
   "$ROOT_DIR/examples/generic-uart-embedded/uart_ping.c" \
   -o "$EXAMPLE_BUILD_DIR/uart_ping"
 
+echo "Building generic GPIO Embedded Linux tool..."
+"${CC:-cc}" \
+  -O2 -g -Wall -Wextra -Wpedantic -Werror -std=c11 -D_POSIX_C_SOURCE=200809L \
+  "$ROOT_DIR/examples/generic-gpio-embedded/gpio_tool.c" \
+  -o "$EXAMPLE_BUILD_DIR/gpio_tool" \
+  -lgpiod
+
 touch "$STATE_DIR/.built"
 
 echo

dev.sh

@@ -13,6 +13,8 @@ I2C_CUSE_BUILD_DIR="$ROOT_DIR/build/adapters/i2c-cuse"
 I2C_CUSE_EXECUTABLE="$I2C_CUSE_BUILD_DIR/vds4e-i2c-cuse"
 UART_PTY_BUILD_DIR="$ROOT_DIR/build/adapters/uart-pty"
 UART_PTY_EXECUTABLE="$UART_PTY_BUILD_DIR/vds4e-uart-pty"
+GPIO_SIM_BUILD_DIR="$ROOT_DIR/build/adapters/gpio-sim"
+GPIO_SIM_EXECUTABLE="$GPIO_SIM_BUILD_DIR/vds4e-gpio-sim"
 LOCK_FILE="${TMPDIR:-/tmp}/vds4e-dev-${UID}.lock"
 SERVER_PID=""
 WEB_PID=""
@@ -140,6 +142,14 @@ cmake \
   -DCMAKE_BUILD_TYPE=Debug
 cmake --build "$UART_PTY_BUILD_DIR" --parallel
 
+echo "Configuring and building the GPIO simulator adapter..."
+prepare_cmake_build_dir "$ROOT_DIR/adapters/gpio-sim" "$GPIO_SIM_BUILD_DIR"
+cmake \
+  -S "$ROOT_DIR/adapters/gpio-sim" \
+  -B "$GPIO_SIM_BUILD_DIR" \
+  -DCMAKE_BUILD_TYPE=Debug
+cmake --build "$GPIO_SIM_BUILD_DIR" --parallel
+
 if [[ "${VDS4E_ADAPTER_AUTH:-pkexec}" == "sudo" ]]; then
   # sudo's default credential cache is terminal-scoped. Keep the server in
   # this terminal session so adapter helpers can use the one authorization
@@ -149,13 +159,15 @@ if [[ "${VDS4E_ADAPTER_AUTH:-pkexec}" == "sudo" ]]; then
     VDS4E_SPI_CUSE_EXECUTABLE="$SPI_CUSE_EXECUTABLE" \
     VDS4E_I2C_CUSE_EXECUTABLE="$I2C_CUSE_EXECUTABLE" \
     VDS4E_UART_PTY_EXECUTABLE="$UART_PTY_EXECUTABLE" \
+    VDS4E_GPIO_SIM_EXECUTABLE="$GPIO_SIM_EXECUTABLE" \
     "$ROOT_DIR/build/rust/debug/vds-server" --config config/vds-server.yaml &
   SERVER_PID=$!
 else
   setsid env \
     VDS4E_SPI_CUSE_EXECUTABLE="$SPI_CUSE_EXECUTABLE" \
     VDS4E_I2C_CUSE_EXECUTABLE="$I2C_CUSE_EXECUTABLE" \
     VDS4E_UART_PTY_EXECUTABLE="$UART_PTY_EXECUTABLE" \
+    VDS4E_GPIO_SIM_EXECUTABLE="$GPIO_SIM_EXECUTABLE" \
     cargo run -p vds-server -- --config config/vds-server.yaml &
   SERVER_PID=$!
   SERVER_OWN_PROCESS_GROUP=true

examples/generic-gpio-embedded/Makefile

@@ -0,0 +1,15 @@
+CC ?= cc
+CFLAGS ?= -O2 -g -Wall -Wextra -Wpedantic -Werror -std=c11 -D_POSIX_C_SOURCE=200809L
+LDFLAGS ?=
+LDLIBS ?= -lgpiod
+
+.PHONY: all clean
+
+all: gpio_tool
+
+gpio_tool: gpio_tool.c
+	$(CC) $(CFLAGS) $(LDFLAGS) $< -o $@ $(LDLIBS)
+
+clean:
+	rm -f gpio_tool
+

examples/generic-gpio-embedded/README.md

@@ -0,0 +1,50 @@
+# Generic GPIO Embedded Linux Tool (`gpio_tool`)
+
+This example application uses the standard Linux `libgpiod` API to inspect, read, drive, and monitor virtual GPIO lines over a `/dev/gpiochipN` character device.
+
+It is designed to work with the VDS4E [`generic-gpio-bank-32`](../../device-models/examples/generic-gpio-bank/) model:
+- **Lines 0–15 (`GPIO0`–`GPIO15`):** Device inputs from the virtual peripheral's perspective. The host drives these lines with `set`; the corresponding `GPIOx_STATE` register updates in VDS4E.
+- **Lines 16–31 (`GPIO16`–`GPIO31`):** Device outputs from the virtual peripheral's perspective. The host reads these lines with `get` or monitors edge transitions with `monitor`.
+
+---
+
+## Build
+
+```bash
+make
+```
+
+To clean build artifacts:
+```bash
+make clean
+```
+
+---
+
+## Usage
+
+### 1. Show Controller Info & Line Table
+```bash
+./gpio_tool -c /dev/gpiochip0 info
+```
+
+### 2. Read Device Output Line
+```bash
+./gpio_tool -c /dev/gpiochip0 get 16
+```
+
+### 3. Drive Device Input Line
+```bash
+./gpio_tool -c /dev/gpiochip0 set 0 1
+```
+
+To keep the line held in state:
+```bash
+./gpio_tool -c /dev/gpiochip0 set 0 1 --hold
+```
+
+### 4. Monitor Edge Transitions (Interrupts / Events)
+```bash
+./gpio_tool -c /dev/gpiochip0 monitor 16
+```
+*(When `GPIO16_STATE` changes via Web UI or API, edge events appear in real time)*